The effect of UV/H2O2 treatment on disinfection by-product formation potential under simulated distribution system conditions.

Advanced oxidation with ultraviolet light and hydrogen peroxide (UV/H(2)O(2)) produces hydroxyl radicals that have the potential to degrade a wide-range of organic micro-pollutants in water. Yet, when this technology is used to reduce target contaminants, natural organic matter can be altered. This study evaluated disinfection by-product (DBP) precursor formation for UV/H(2)O(2) while reducing trace organic contaminants in natural water (>90% for target pharmaceuticals, pesticides and taste and odor producing compounds and 80% atrazine degradation). A year-long UV/H(2)O(2) pilot study was conducted to evaluate DBP precursor formation with varying water quality. The UV pilot reactors were operated to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for DBP precursor formation. Two process waters of differing quality were used as pilot influent, i.e., before and after granular activated carbon adsorption. DBP precursors increased under most of the conditions studied. Regulated trihalomethane formation potential increased through the UV/H(2)O(2) reactors from 20 to 118%, depending on temperature and water quality. When Post-GAC water served as reactor influent, less DBPs were produced in comparison to conventionally treated water. Haloacetic acid (HAA5) increased when conventionally treated water served as UV/H(2)O(2) pilot influent, but only increased slightly (MP lamp) when GAC treated water served as pilot influent. No difference in 3-day simulated distribution system DBP concentration was observed between LP and MP UV reactors when 80% atrazine degradation was targeted.

The effect of UV/H2O2 treatment on biofilm formation potential.

Greater Cincinnati Water Works (GCWW) evaluated the efficacy of ultraviolet light/hydrogen peroxide advanced oxidation (UV/H(2)O(2)) for reducing trace organic contaminants in natural water with varying water qualities. A year-long UV/H(2)O(2) pilot study was conducted to examine a variety of seasonal and granular activated carbon (GAC) breakthrough conditions. The UV pilot-scale reactors were set to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for by-product formation. Because hydroxyl radicals react non-selectively with organic compounds, unintended by-product formation occurred. Total assimilable organic carbon (AOC) concentration increased through the reactors from 14 to 33% on average, depending on water quality. Natural organic matter (NOM) contains the precursors for AOC production, so when post-GAC water (versus conventionally treated water) served as reactor influent, less AOC was produced. No appreciable difference in AOC concentration was observed between LP and MP UV reactors. The Spirillum strain NOX fraction of the AOC increased from 50 to 65% on average, depending on the quality of the water. The increase in this fraction of AOC occurred because oxidation of NOM yielded smaller more assimilable organic compounds such as organic acids that are necessary for NOX growth. The Pseudomonas fluorescens strain P17 AOC concentration increased only when conventionally treated plant water was used as pilot influent. This organism thrives in waters of differing organic energy sources, but does not thrive well in carboxylic acids alone. The CONV water had more overall TOC that could contribute to higher P17 AOC counts. Biofilm coupon studies indicated that biofilms with greater heterotrophic plate counts were observed in the granular activated carbon (GAC) effluent streams receiving UV/H(2)O(2) pre-treatment. Biofilm coupon studies additionally indicated that the effluent stream of the GAC column proceeded by the MP reactor exhibited more viable biofilm than the other GAC effluent streams based on an ATP-bioluminescence method. The increased viability of the biofilm produced by the MP UV reactor is likely a result of the multiple UV wavelengths and higher energy input characteristic of this technology.

Formation and removal of genotoxic activity during UV/H(2)O(2)-GAC treatment of drinking water.

The objective of this study was to determine the genotoxic activity of water after UV/H(2)O(2) oxidation and GAC filtration. Pre-treated surface water from three locations was treated with UV/H(2)O(2) with medium pressure (MP) lamps and passed through granulated activated carbon (GAC). Samples taken before and after each treatment step were extracted and concentrated by solid phase extraction (SPE) and analyzed for genotoxicity using the Comet assay with HepG2 cells and the Ames II assay. The Comet assay showed no genotoxic response in any of the samples. In the Ames II, no genotoxic response was obtained with the TAMix (a mix of six strains), but the TA98 strain showed an increase in genotoxic activity after MP-UV/H(2)O(2) for all three locations. GAC post treatment effectively reduced the activities to control levels at two of the three locations and to below the level of the pre-treated water at one site. The results indicate that UV/H(2)O(2) treatment may lead to the formation of genotoxic by-products, which can be removed by subsequent GAC filtration.

A study of events in chick cells infected with human adenovirus type 5 and their relationship to the induction of interferon.

In an attempt to define the molecular events involved in induction of interferon, various parameters of chick cells infected with human adenovirus type 5 were analysed. It was shown by digestion with various proteolytic enzymes and by disruption of the purified virus that induction of interferon requires the interaction of infectious virus with the chick cells. Analysis of adenovirus-infected chick cells by immunological and biochemical techniques indicated that most of the cells produce some virus-specific components, and that temperature sensitive mutants which fail to induce interferon at the restrictive temperature fail to synthesize late components at that temperature. However, since it has been shown that interferon can be induced in the absence of DNA synthesis, these studies conclude that interferon induction results from an early interaction between virus (or virus product) and chick cells and moreover that this interaction is also necessary for the synthesis of virus DNA in this system.

Further investigations on the mode of entry of vaccinia virus into cells.

Earlier results indicating that vaccinia virus entered L cells by a process of direct fusion between the virus envelope and the plasma membrane of the cell have been confirmed and extended using immuno-ferritin conjugates to locate virus antigens on the host cell surface. After fusion, components of the virus envelope become rapidly dispersed in the plasma membrane. Fusion has also been observed as the predominant mode of entry of vaccinia virus into HeLa cells.

Mechanism of interferon action: further evidence for transcription as the primary site of action in simian virus 40 infection.

Interferon inhibits the replication of simian virus 40 (SV40) in monkey cells and reduces markedly the formation of both early virus protein (i.e. SV40 T antigen) and early SV40 RNA. This suggests that in SV40 infection interferon acts primarily by inhibiting transcription. To test this conclusion further, we examined alternative mechanisms which might explain these results and made the following observations. (1) The quantity of input SV40 DNA in the nucleus 24 h post infection (p.i.) was the same in interferon-treated and control cells. Thus interferon does not appear to diminish the quantity of SV40 DNA template available for transcription. (2) Chemical inhibitors of protein synthesis did not mimic the selective inhibition of early SV40 RNA formation induced by interferon, indicating that the transcription of early SV40 RNA is not dependent upon the prior synthesis of any virus-induced protein. Thus a block in translation cannot readily explain the reduced formation of early SV40 RNA in interferon-treated cells. (3) Fractionation of SV40 infected cells after a one-hour labelling period showed that interferon produced a comparable reduction in the quantity of early SV40 RNA in the nucleus and the cytoplasm. Thus the observed inhibition of early SV40 RNA is not due solely (if at all) to enhanced cytoplasmic degradation. These results indicate that the primary effect of interferon in SV40 infected monkey cells is either to inhibit the transcription of early virus RNA or to enhance its turnover in the nucleus.

The effect of interferon on the formation of virus polyribosomes in L cells infected with vaccinia virus.

The effect of interferon treatment of mouse L cells on the fate of virus messenger RNA following infection with vaccinia virus has been studied. The polyribosomes of interferon-treated, infected cells are found to be disaggregated and it is proposed that htis results from inhibition of the initiation of virus polypeptide snythesis. Evidence is presented that inhibition of polypeptide chain elongation also occurs. The block in initiation appears to be due to the failure of the small ribosome subunit to attach to the virus messenger ribonucleoprotein complex. The translation of the different vaccinia messenger species is inhibited to a comparable extent.

The formation of virus polyribosomes in L cells infected with vaccinia virus.

The fate of early virus messenger RNA in the cytoplasm of vaccinia-infected L cells has been studied during the first hour after infection. The RNA is made in the virus core structure from which it is rapidly released. It accumulates in the polyribsome fraction, where at least 75% is bound to ribosomes through an EDTA-sensitive link. Three distinct structures have been identified as possible intermediates in virus polyribosome formation. The first is a ribonucleoprotein complex (RNP) in which virus RNA is associated with cellular proteins. A complex having apparently similar properties, is formed when virus RNA is added to a cytoplasmic extract in vitro. The other two structures may consist of an RNP moiety associated with the small ribosomal subunit, or with a single ribosome. At least part of the RNA isolated as RNP appears to be a precursor of the virus messenger found in polyribosomes.

Mechanism of interferon action: inhibition of viral messenger ribonucleic acid translation in L-cell extracts.

Encephalomyocarditis (EMC) virus ribonucleic acid (RNA) stimulated the incorporation of (14)C-amino acids into polypeptides in cell-free systems using preincubated S10 extracts from L cells. Incorporation was linear for over 2 hr. Analysis of the tryptic peptides derived from the polypeptide products formed in response to EMC RNA showed them to be virus specific. The major product, a polypeptide of 140,000 in molecular weight, migrated on sodium dodecyl sulfate-polyacrylamide gels with one of the virus-specific polypeptides present in EMC-infected cells. A minor component of molecular weight about 230,000 may correspond to the product of complete translation of the EMC virus genome. Little or no effect of interferon or vaccinia virus infection was observed in the preincubated, cell-free system. The EMC RNA-stimulated incorporation of (14)C-amino acids into polypeptides was not inhibited in extracts derived from L cells early in virus infection, from interferon-treated cells, or from cells subjected to both treatments. Interferon treatment did appear to have a slight inhibitory effect on chain elongation in this system. However, treatment of cells with highly purified interferon before virus infection caused a decrease of about 80% in the capacity of non-preincubated cell extracts to translate added EMC RNA. This effect did not extend to the translation of polyuridylic acid and could be reversed by preincubation of the extracts at 37 C for 20 min. The inhibition of translation was manifest at interferon concentrations as low as 5IU/ml, and in this respect closely paralleled the inhibition of virus growth. Inactivation of the antiviral activity of the interferon by heating or digestion with trypsin also abolished the effect on cell-free protein synthesis. The EMC-specific polypeptides formed in reduced amounts in extracts of interferon-treated vaccinia-infected cells were smaller than those formed in extracts of untreated, vaccinia-infected cells. Thus, inhibition of initiation or elongation of polypeptides, or both, can be demonstrated in cell-free systems employing non-preincubated extracts from interferon-treated, virus-infected cells. These results indicate that antiviral activity of interferon is directed against the translation of viral messenger RNA.